2008 GMC Sierra 1500 Pickup Owner's Manual - Page 155

Reading Lamps If your vehicle has reading lamps they are located on the overhead console. To turn on the reading lamps, press the button located next to each lamp. To turn them off, press the button again. Your vehicle may also have reading lamps in other locations. To turn the lamps on or off, press the button located next to the lamp. If your vehicle has a DVD Rear Seat Entertainment (RSE) system, press the lamp lenses to turn the lamps on or off. The lamps are fixed and cannot be adjusted. Electric Power Management The vehicle has Electric Power Management (EPM) that estimates the battery's temperature and state of charge. It then adjusts the voltage for best performance and extended life of the battery. When the battery's state of charge is low, the voltage is raised slightly to quickly put the charge back in. When the state of charge is high, the voltage is lowered slightly to prevent overcharging. If the vehicle has a voltmeter gage or a voltage display on the Driver Information Center (DIC), you may see the voltage move up or down. This is normal. If there is a problem, an alert will be displayed. The battery can be discharged at idle if the electrical loads are very high. This is true for all vehicles. This is because the generator (alternator) may not be spinning fast enough at idle to produce all the power that is needed for very high electrical loads. A high electrical load occurs when several of the following loads are on: headlamps, high beams, fog lamps, rear window defogger, climate control fan at high speed, heated seats, engine cooling fans, trailer loads, and loads plugged into accessory power outlets. Cargo Lamp The cargo lamps come on by turning the instrument panel brightness control knob to the farthest clockwise position. This knob is located on the instrument panel and also turns on the dome lamps. The cargo lamp can be used if more light is needed in the cargo area of the vehicle or in the top-box storage units. 3-19